180 THE MYXOMYCETES OF PICTOLJ COUNTY. MOORE. 



free or (2) externally on columnar or membranous sporophores 

 or (3) in closed capsules or sporangia. In germinating the 

 spores produce amoeboid bodies whicih pass through a ciliated 

 stage and which eventually fuse to form a multinuclear proto- 

 plasmic mass, the plasmodium, which gives rise to the fructifi- 

 cations. 



Sub-class 1. PHYTOMYXIN^E. Mature fruit bodies 

 converted into an aggregation of free -spores. Parasitic in cells 

 of living plants. 



Sub-class 2. EXOSPOBE.E. Spores formed superficially 

 on membranous or columnar sporophores. Saprophytic. 



Sub-class 3. MYXOGASTKES. Spores formed within 

 sporangia. Saprophytic. 



PHYTOMYXIN^E Schroter. 



Parasitic in the cells of living plants. The spores are formed 

 by tohe simultaneous division of the mature plasmodium and lie 

 free in the cells of the host. 



Genus., Plasmodiophora Woronin. 



The only representation of the genus and sub-class which 

 has come under my observation is : 



1. Plasmodiophora brassicce Woronin. This species is 

 parasitic on various cruciferse such a,s the turnip, cabbage, rape 

 and kale, producing in these plants the disease popularly known 

 as " Club root." T|he roots of infected plants exhibit irregular 

 and distorted growth, become covered with irregular protuber- 

 ances and swellings and eventually decay. A section through 

 one of these swellings shews the enlarged parenchymatous cells 

 almost completely filled either with plasmodium ( ?) of the 

 parasite or with the spores. These are spherical and about 1.5/* 

 in diameter. 



.. What is probably the same parasite also occurs here on spe- 

 cies of wild mustard and is pretty generally distributed through- 



